Elbow arthroplasty instrumentation and surgical procedure

ABSTRACT

A method and apparatus for modifying the distal end of the humerus deformed by injury or disease in preparation for fixation of an elbow joint replacement. A through hole is first formed in the superior aspect of the olecranon fossa communicating with the humeral canal. A stem member which extends from the platform of a distal cut guide tool is received through the hole and extends into the humeral canal. The distal cut guide tool is held so that the platform is generally coplanar with the junction of the medial epicondyle and the trochlea with proper inclinations, both in an anterior view and in a lateral view. Thereupon, a first resected surface is formed by sawing, using as a guide, a planar guiding surface provided on the platform. With removal of the distal cut guide tool, a broach and chamfer cut guide tool having a plurality of saw guide slots is positioned on the first resected surface and additional cuts are made with the aid of the latter tool to form a wedge of bone onto which a humeral prosthesis can be impacted.

This is a divisional of copending application Ser. No. 07/401,634 filedon 8/31/89, now U.S. Pat. No. 4,927,422.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention relates to a method and apparatus for modifyingthe distal end of a humerus deformed by disease or injury in preparationfor implanting an elbow joint replacement.

b. Description of the Prior Art

The success of total hip and knee replacement in recent years has beenattributed largely to precise fit of the implant. The need for exactingplacement of the prosthetic components intraoperatively has led to thedesign of sophisticated instrumentation to enable even the mosttechnically embarrassed surgeons to perform successful jointreplacement.

Typical of such known instrumentation are the disclosures presented inU.S. Pat. Nos. 4,791,919 to Elloy et al, 4,736,737 to Fargie et al, and3,782,373 to Smythe.

Elloy et al provide instrumentation for use in the surgical implantationof a total knee prosthesis and is intended for use on both the tibia andon the femur. Fargie et al disclose a cutting jig for use in obtainingan accurate tibial resection in the course of a total knee prosthesisimplantation procedure. Smythe discloses a jig for forming one or moreholes accurately positioned in the femur for the purpose ofaccommodating suitable fasteners to anchor the femoral component of ahip joint.

Other joints beside the hip and knee, however, still require expertcarpentry skill and superb craftsmanship on the part of the surgeon. Thesurface replacement total elbow, for example, has long been consideredone of the most demanding and time consuming total joint replacementsdue to the difficulty of handiwork required to place the humeralcomponent in a biomechanically exact position in the bone.

The invention disclosed herein provides a set of instruments and asurgical technique that, when used properly, ensures accurate placementof the humeral component in reference to the long axis of the humerusand provides a non talent specific method for resection of bone throughthe use of cutting guides. Intramedullary alignment, previouslyconsidered impossible on the elbow, can now be achieved on a routinebasis.

SUMMARY OF THE INVENTION

It was in light of the prior art as just described that the presentinvention has been conceived and is now reduced to practice. Broadlyspeaking, the invention relates to a method and apparatus for modifyingthe distal end of the humerus deformed by injury or disease inpreparation for fixation of an elbow joint replacement. A through holeis first formed in the superior aspect of the olecranon fossacommunicating with the humeral canal. A stem member which extends fromthe platform of a distal cut guide tool is received through the hole andextends into the humeral canal. The distal cut guide tool is held sothat the platform is generally coplanar with the junction of the medialepicondyle and the trochlea with proper inclinations, both in ananterior view and in a lateral view. Thereupon, a first resected surfaceis formed by sawing, using as a guide, a planar guiding surface providedon the platform. Following removal of the distal cut guide tool, abroach and chamfer cut guide tool provided with a plurality of saw guideslots is positioned on the first resected surface and additional cutsare made with the aid of the latter tool to form a wedge of bone ontowhich a humeral prosthesis can be impacted.

More specifically, the distal cut guide tool includes a long slender rodwith a platform attached at one end. The orientation of the platform issuch that it makes an angle with the rod that is equal to the valgusangle of the elbow in the anterior/posterior view. In the lateral view,the angle of the platform, relative to the rod is equal to the anteriorslope of the elbow joint. When the distal cut guide tool is passed downthe intramedullary canal of the humerus, the platform serves as ascaffold upon which an oscillating saw is used to make the first boneresection.

The broach and chamfer cut guide tool is used after the distal cut guidetool has been removed from the humerus. It comprises an analogousintramedullary rod that blends into a broach which has similardimensions as the stem of the humeral component implant. Secured to theend of the broach is a chamfer guide block. When the broach and chamfercut guide tool is tapped into the canal of the humerus, the chamferguide block lies flush with the first distal resection. The slots in thechamfer guide block capture the blade of an oscillating saw to orientthe final resection of bone necessary to achieve the goal of theinvention.

Although, as noted above, intramedullary alignment instrumentation hasbeen used successfully for years in the knee, it was previously thoughtimpossible to achieve the same success with other joints due to the factthat no entrance to the intradmedullary canal could be made withoutdestroying the articular surface. However, a step wise surgicalprocedure is disclosed herein that presents a method by which this ispossible for the elbow with the use of the specifically designedinstrumentation. To this end, a hole in the distal humerus must beprecisely located in the posterior and lateral views of the bone.Posterior location of the hole is in the superior aspect of theolecranon fossa slightly lateral of the perceived bone centerline. Theplacement of the hole in the lateral view allows the axis of the drillor burr to just touch the posterior aspect of the olecranon sulcus. Arod passed through such a hole will exactly follow the axis of the bone.

According to the invention, the intramedullary distal cut guide tool ispassed through this hole and into the humeral canal until the saw guideplatform is at the level at which the medial epicondyle forms a junctionwith the trochlea. This ensures that the optimal amount of bone isresected initially to restore the anatomical center of rotation of thejoint. The resulting cut sets the valgus orientation as well as theanterior slope with respect to the axis of the humerus. Once the distalcut guide is removed, the broach and chamfer and guide tool is passeddown the canal and tapped down until the chamfer guide block sets flushwith the initial resection. When this is achieved, the stem of theimplant has been exactly oriented with the finish chamfer resections.The slots in the chamfer guide block capture the blade of an oscillatingsaw to enable precise finish cuts to be made.

Thus, an improved method and instrumentation is herein described withwhich intramedullary location of resection surfaces can easily beemployed for humeral component placement in total elbow arthroplasty.The instruments and surgical protocol are simple to use and ensureprecise location and placement of the humeral component to ensurerestoration of joint biomechanics.

Other and further features, advantages, and benefits of the inventionwill become apparent in the following description taken in conjunctionwith the following drawings. It is to be understood that the foregoinggeneral description and the following detailed description are exemplaryand explanatory but are not to be restrictive of the invention. Theaccompanying drawings which are incorporated in and constitute a part ofthis invention, illustrate one of the embodiments of the invention, and,together with the description, serve to explain the principles of theinvention in general terms. Like numerals refer to like parts throughoutthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a detail posterior view illustrating the distal end of adiseased or injured humerus to which the first step of the novelprocedure of the invention has been applied;

FIG. 2 is a detail posterior view of the humerus, similar to FIG. 1,illustrating the use of a first novel instrument, namely, a distal cutguide tool, for purposes of the novel procedure of the invention;

FIG. 3 is a detail medial view of the humerus and of the distal cutguide tool positioned as illustrated in FIG. 2;

FIG. 4 is a perspective view of the entire distal cut guide tool, partsof which are illustrated in FIGS. 2 and 3;

FIG. 5 is a detail medial view of the humerus similar to FIG. 3 butillustrating a subsequent step of the procedure of the invention;

FIG. 6 is a perspective view of the entire broach and chamfer cut guidetool intended for use with the novel procedure of the invention;

FIG. 7 is a posterior view of the distal end of the humerus, similar toFIGS. 1 and 2, but in which the bone is formed with a resected surfaceand to which a second tool, namely a broach and chamfer cut guide tool,is being applied;

FIG. 8 is a detail medial view, similar to FIG. 3, illustrating thebroach and chamfer cut guide tool in its operational position on thedistal end of the humerus;

FIG. 9 is an enlarged detail medial view of parts illustrated in FIG. 8and depicting a further step in the procedure of the invention;

FIG. 10 is a detail perspective view of the distal end of the humeruswhich has been modified in accordance with the procedure of theinvention to receive a humeral prosthesis and depicted about to receivethe humeral component;

FIG. 10A is a detail perspective view of the distal end of the humerus,similar to FIG. 10, but modified to receive a modified construction ofhumeral prosthesis;

FIG. 11 is a top plan view of a humeral prosthesis; and

FIG. 12 is a cross section view taken generally along line 10--10 inFIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turn now to the drawings and initially to FIG. 1 which is illustrativeof the distal end of a humerus 20 which exhibits an undesirable geometryby reason of injury or disease. For aid in orientation, FIG. 1 is aposterior view which depicts the medial epicondyle 22, the lateralepicondyle 24 and the olecranon fossa 26 of the humerus. The presentinvention is directed toward a surgical procedure, and instrumentation,for modifying the geometry existing at the distal end of the humerus 20in preparation for fixation thereto of an appropriate prosthesisenabling the elbow joint to substantially regain its former ability tofunction.

The procedure of the invention is initiated by forming a through hole 28in the superior aspect of the olecranon fossa 26 by using a drill orburr in a customary fashion. The hole 28 may be approximately 10 mm indiameter and extends through the bone so as to communicate with thehumeral canal 30 (FIGS. 2 and 3). It may be noted that the hole 28should be slightly laterally disposed in order to be aligned with theaxis of the humerus 20.

The next step in the procedure is depicted in FIGS. 2 and 3 and theinstrument used for this step, namely, a distal cut guide tool 32 isillustrated in its entirety in FIG. 4. The guide tool 32 includes aplatform 34 having a planar guide surface 36 for guiding a saw blade 38(FIG. 5) for forming a resected surface 40 (FIG. 3) at the distal end ofthe humerus 20. A long, slender, stem member 42 is integral with theplatform 34 and extends away from the platform. The stem member 42 isinserted, through the hole 28, into the humeral canal 30 until a medialedge 44 (FIGS. 3 and 4) is at the level of a junction 46 of the medialepicondyle 22 and the trochlea 48 of the humerus 20. The guide tool 32is constructed such that there is a preestablished angular relationshipbetween the platform 34 and the stem member 42. In keeping with thisrelationship, when the medial edge 44 is positioned at the junction 46,the guide surface 36 lies in a plane which is parallel to the anatomicalaxis of rotation of the elbow joint, that is, parallel to the axis ofrotation of the previously healthy articular surface. To achieve thisrelationship, the guide surface 36 is inclined relative to the stemmember 42 when the stem member is positioned within the humeral canal 30and aligned with the longitudinal axis of the humerus 20. According tothis relationship, in an anterior/posterior view, the guide surface 36assumes the normal valgus angle 49 (FIG. 2) of a healthy humerus, andsuch that, in a lateral view, the guide surface 36 generally assumes theanterior angle of inclination 50 (FIG. 3) of a healthy humerus.

With the distal cut guide tool 32 positioned as illustrated in FIGS. 2and 3, the surgeon advances a saw 51 operating the saw blade 38 so thatthe saw blade is coplanar and contiguous with the guide surface 36. Thesaw blade 38 is then advanced along the surface 36 into cuttingengagement with the distal end of the humerus 20 thereby separating adistal segment 52 (FIGS. 3 and 5) from the remainder of the humerus 20and forming the resected surface 40.

Thereupon, the guide tool 32 is withdrawn from the humeral canal 30 andremoved from the humerus 20.

Upon removal of the distal segment 52 and of the guide tool 32 from theenvirons of the humerus 20, a second instrument, namely a broach andchamfer cut guide tool 54, is inserted into the humeral canal 30 via thethrough hole 28. The broach and chamfer cut guide tool 54 isparticularly well illustrated in FIG. 6. It includes a guide block 56and a guide stem 58 integral with and extending away from the guideblock. The region of the guide stem 58 nearest the guide block 56includes a broach 60 for selectively modifying the region surroundingthe through hole 28 so as to accommodate the stem of a prosthesis, ifdesired.

According to the novel surgical procedure of the invention, viewing FIG.7, the stem 58 of the tool 54 is inserted through the hole 28 into thehumeral canal 30 until the broach 60 engages the hole 28 of the humerus20. The broach is "worked", that is, moved back and forth in thedirections of a two ended arrow 62 for the purpose of removing excessbone from the region of the hole. In performing this operation, it isdesirable to bias the broach toward the lateral side of the humerus,since if it "works" medially, the bone will not allow a proper valgustilt of the tool 54. Indeed, it may be necessary or desirable to burrcortical bone surrounding the hole 28 adjacent to the medial, lateral,or anterior edges of the broach to aid in the insertion of the tool 54.

In any event, once the hole 28 has been appropriately modified, the tool54 should be capable of being fully inserted into the humerus 20 in themanner illustrated in FIG. 8. When the tool 54 assumes its fully seatedcondition, a planar undersurface 64 of the guide block 56 iscontiguously and engageably received on the resected surface 40.

As seen particularly well in FIG. 6, the guide block 56 is formed with apair of spaced parallel anterior/posterior guide slots 66, 68 which liein planes generally perpendicular to that of the undersurface 64. Oneset of the guide slots 66, 68 are formed in one slotted member 70 andanother set of the slots 66, 68 are formed in another slotted member 72,a solid cnetral member 74 being integral with, but separating theslotted members 70 and 72. It is from the solid central member 74 thatthe guide stem 58 extends. A pair of chamfer guide slots 76, 78 are alsoformed discontinuously in the block 56 in the manner of the guide slots66, 68. However, the guide slots 76, 78 are angularly disposed relativeto the undersurface 64 and relative to each other.

With the guide block 56 resting firmly on the resected surface 40 asseen in FIG. 8, the saw 50 and its associated blade 38 are used onceagain to make cuts into the bone at the distal end of the humerus, onthis occasion guided by the slots 66, 68, and 76, 78 (see FIG. 9). Cutsinto the bone which result when the blade 38 follows the slots 66, 68establish the width of a bone mesa 80 (FIGS. 9 and 10) onto which aprosthesis to be described can be affixed. The purpose for the slots 76,78, in contrast, are to form chamfers 82 along the length of the bonemesa 80 which serve to aid in the reception of the prosthesis as it isbrought into engagement with the distal end of the humerus 20.

Since the guide block 56 does not permit continuous cuts to be made withthe slots 66, 68, and 76, 78, the next step in the procedure is toremove the tool 54 from the humerus 20, then to complete the cuts in theregion which the central member 74 previously occupied. Thereupon,viewing FIG. 7, the bone is cut generally along surfaces 84, 86resulting in segments 88, 90 to be removed. The depth 91 of the cutresulting in the surfaces 84, 86 is determined by the depth of theprosthesis intended to be mounted on the distal end of the humerus 20.The operation of forming the surfaces 84, 86 in order to remove thesegments, 88, 90 may be performed in a customary fashion by means of aburr, or in any other suitable fashion.

Also, as particularly well seen in FIG. 6, the central member 74 of theguide block 56 is provided with a drilled and tapped blind bore 92. Thetapped bore is intended to receive, if desirable, a handle 94 whichincludes an enlarged gripping head 96 and an integral threaded shaft 98threadedly engageable with the bore 92. The handle 94 may be ofsubstantial aid to the surgeon in manipulating the tool 54 during theprocedure just described.

Turn now to FIGS. 11 and 12 which are generally illustrative of ahumeral prosthesis 104 intended for mounting on the bone mesa 80. Itwill be appreciated that the prosthesis 104 may be of a known design asis the shape of the bone mesa 80 upon which it is to be affixed. Thenovelty residing in the invention relates to the method and specialinstrumentation employed in forming the bone mesa 80. In any event, theprosthesis 104 is seen to be formed with a cavity 106 which is formedfor congruent reception on the bone mesa 80. The cavity 106 is formedwith chamfer portions 108 which matingly engage with the chamfers 82 onthe bone mesa 80 when the prosthesis is affixed thereto.

One embodiment of a completed implant is illustrated in FIG. 10. Amodified version is illustrated in FIG. 10A which includes an integralstem 110 extending through the hole 28 and into the humeral canal. Toaccommodate the stem 110, it may be necessary to form a V-shaped wedgeresection of bone 112 from distal to proximal through the olecranonfossa and into the distal humeral canal through the opening 28. It isrecommended that a stemmed humeral component be used in instances ofrheumatoid arthritis in which osteoporosis is present and fracture of ahumeral fixation might be a concern.

While preferred embodiments of the invention have been disclosed indetail, it should be understood by those skilled in the art that variousother modifications may be made to the illustrated embodiments withoutdeparting from the scope of the invention as described in thespecification and defined in the appended claims.

What is claimed is:
 1. A distal cut guide tool for use in a surgicalprocedure of modifying injured or diseased geometry existing at thedistal end of a humerus in preparation for fixation thereto of areplacement for an elbow joint comprising:a platform having a peripheraledge and a planar guide surface for guiding a saw blade for forming aresected surface at the distal end of the humerus lying in a planetransverse to the longitudinal axis of the humerus; a stem memberintegrally connected to said platform and extending away form saidperipheral edge and away form said planar guide surface, said stemmember being receivable through a hole formed in the superior aspect ofthe olecranon fossa of the humerus and extending into the humeral canaland generally aligned with the longitudinal axis of the humerus;whereby, when said stem member is received in the humeral canal andaligned with the longitudinal axis of the humerus, said platform ispositioned offset from said longitudinal axis adjacent the distal end ofthe humerus and said planar guide surface lies in a plane parallel tothe anatomical axis of rotation of the elbow joint and said planar guidesurface is inclined relative to said stem member such that, in ananterior view, it generally assumes the normal valgus angle of a healthyhumerus and such that, in a lateral view, it generally assumes theanterior angle of inclination of a healthy humerus.
 2. A distal cutguide tool for use in a surgical procedure of modifying injured ordiseased geometry existing at the distal end of a long bone inpreparation for fixation thereto of a replacement joint at the distalend comprising:a platform having a peripheral edge and a planar guidesurface for guiding a saw blade for forming a resected surface at thedistal end of the long bone lying in a plane transverse to thelongitudinal axis of the long bone; a stem member integrally connectedto said platform and extending away from said peripheral edge and awayfrom said planar guide surface, said stem member being receivablethrough a hole formed in the superior aspect of the distal end of thelong bone and extending into the intramedullary canal and generallyaligned with the longitudinal axis of the long bone; whereby, when saidstem member is received in the intramedullary canal and aligned with thelongitudinal axis of the long bone, said platform is positioned offsetfrom said longitudinal axis adjacent the distal end of the long bone andsaid planar guide surface lies in a plane parallel to the anatomicalaxis of rotation of the joint and said planar guide surface at thedistal end thereof is inclined relative to said stem member such that,in an anterior view, it generally assumes the normal valgus angle of ahealthy long bone and such that, in a lateral view, it generally assumesthe anterior angle of inclination of a healthy long bone.